• Journal of Korea Planning Association
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• v.54 no.2
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• pp.93-108
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• 2019

This study examines the relationship between three-dimensional urban built environment and urban surface temperature using LANDSAT 8 satellite image data in Seoul city. The image was divided into 600m×600m grid units as an unit of analysis. Due to the high level of spatial dependency in surface temperature, this study uses spatial statistics to take into account spatial auto-correlation. The spatial error model shows the best goodness of fit. The analysis results show that the three-dimensional built environment and transport environment as well as natural environment have statistically significant associations with surface temperature. First, natural environment variables such as green space, streams and river, and average elevation show statistically significant negative association with surface temperature. Second, the building area shows a positive association with surface temperature. In addition, while sky view factor (SVF) has a positive association with surface temperature, surface roughness (SR) shows a negative association with it. Third, transportation related variables such as road density, railway density, and traffic volume show positive associations with surface temperature. Moreover, this study finds that SVF and SR have different effects on surface temperature in regard to the levels of total floor areas in built environment. The results indicate that interactions between floor area ratio (FAR) and three-dimensional built environmental variables such as SVF and SR should be considered to reduce urban surface temperature.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.27 no.3
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• pp.175-180
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• 2021

Although it has recently been regulated for use as an eco-friendly policy in Korea, the use of EPS (Expanded Polystyrene) cooling boxes, which are used as cold chain delivery insulation boxes for fresh agricultural and livestock products, is also increasing rapidly as e-commerce logistics such as delivery have increased rapidly due to COVID-19. Studies were conducted to optimize the EPS cooling container through internal air heat flow of CFD (Computational Fluid Dynamics) analysis and FEM (Finite Element Method) random vibration analysis using domestic PSD (Power Spectral Density) profile of the EPS cooling box to which the refrigerant is applied in this study. In the analysis of the internal air heat flow by the refrigerant in the EPS cooling box, the application of vertical protrusions inside was excellent in volume heat flow and internal air temperature distribution. In addition, as a result of random vibration analysis, the internal vertical protrusion gives the rigid effect of the cooling box, so that displacement and stress generation due to vibration during transport are smaller than that of a general cooling container without protrusion. By utilizing the resonance point (frequency) of the EPS cooling box derived by the Model analysis of ANSYS Software, it can be applied to the insulation and cushion packaging design of the EPS product line, which is widely used as insulation and cushion materials.

• Journal of Electrochemical Science and Technology
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• v.12 no.4
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• pp.458-464
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• 2021

Lithium ion batteries (LIBs) is a kind of rechargeable secondary battery, developed from lithium battery, lithium ions move between the positive and negative electrodes to realize the charging and discharging of external circuits. Zeolitic imidazolate frameworks (ZIFs) are porous crystalline materials in which organic imidazole esters are cross-linked to transition metals to form a framework structure. In this article, ZIF-67 is used as a sacrificial template to prepare nano porous carbon (NPC) coated cobalt nanoparticles. The final product Co/NPC composites with complete structure, regular morphology and uniform size were obtained by this method. The conductive network of cobalt and nitrogen doped carbon can shorten the lithium ion transport path and present high conductivity. In addition, amorphous carbon has more pores that can be fully in contact with the electrolyte during charging and discharging. At the same time, it also reduces the volume expansion during the cycle and slows down the rate of capacity attenuation caused by structure collapse. Co/NPC composites first discharge specific capacity up to 3115 mA h/g, under the current density of 200 mA/g, circular 200 reversible capacity as high as 751.1 mA h/g, and the excellent rate and resistance performance. The experimental results show that the Co/NPC composite material improves the electrical conductivity and electrochemical properties of the electrode. The cobalt based ZIF-67 as the precursor has opened the way for the design of highly performance electrodes for energy storage and electrochemical catalysis.

• Nuclear Engineering and Technology
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• v.53 no.5
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• pp.1676-1685
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• 2021

We develop a new high-fidelity multiphysics model to simulate boron chemistry in the porous Chalk River Unidentified Deposit (CRUD) deposits. Heat transfer, capillary flow, solute transport, and chemical reactions are fully coupled. The evaporation of coolant in the deposits is included in governing equations modified by the volume-averaged assumption of wick boiling. The axial offset anomaly (AOA) of the Seabrook nuclear power plant is simulated. The new model reasonably predicts the distributions of temperature, pressure, velocity, volumetric boiling heat density, and chemical concentrations. In the thicker CRUD regions, 60% of the total heat is removed by evaporative heat transfer, causing boron species accumulation. The new model successfully shows the quantitative effect of coolant evaporation on the local distributions of boron. The total amount of boron in the CRUD layer increases by a factor of 1.21 when an evaporation-driven increase of soluble and precipitated boron concentrations is reflected. In addition, the concentrations of B(OH)₃ and LiBO₂ are estimated according to various conditions such as different CRUD thickness and porosity. At the end of the cycle in the AOA case, the total mass of boron incorporated in CRUD deposits of a reference single fuel rod is estimated to be about 0.5 mg.

• Journal of Korea Trade
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• v.23 no.7
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• pp.34-44
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• 2019

Purpose - The purpose of this study is to present what the port of Pyeongtaek, the hub of Korean trade with China, should improve in the current situation, wherein the e-commerce trade volume between Korea and China is increasing due to the development of online technology. Design/methodology - In this study, through prior research and expert interviews on e-commerce and port activation between borders, we derived the main improvement factors for 1) Administration and Systems, 2) Facilities, 3) Transport, and 4) Manpower, and selected 12 detailed variables for the major improvement factors. To identify the relative importance of the major improvement factors, the Analytic Hierarchy Process (AHP) method was applied, and a survey was conducted among 15 related experts. Findings - As a result, among the 12 detailed variables, Composition of Association (0.267) was the first factor to be improved, followed by Incentive Support (0.143) and E-Commerce Cluster (0.131). Based on these analyses, the main implications of this study are, first, in the current situation where the cross-border e-commerce market is growing, Pyeongtaek Port needs to form a consultative body among the government, local governments, and related businesses in connection with cross-border e-commerce and develop various support policies for the e-commerce market. Second, it will have to be able to provide differentiated services from competing ports by establishing e-commerce market-oriented clusters. Originality/value - In existing related studies, various improvements were presented to revitalize trade in line with the growth of the cross-border e-commerce market. However, with regard to most cross-border e-commerce businesses, one-dimensional improvement measures, such as improvement of payment systems, improvement of customs clearance services, and promotion of human resources, are presented in a piecemeal manner. In other words, none of the studies have proposed the importance and priority of each measure in terms of both the forward-looking and efficient allocation of resources, which is the purpose of this study. Therefore, this study contributed politically, practically, and academically by presenting countermeasures for ports to revitalize cross-border e-commerce and presenting strategic priorities using quantitative analysis methods.

• Ecology and Resilient Infrastructure
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• v.9 no.3
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• pp.141-153
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• 2022

In this study, a numerical model of debris flow considering driftwood and entrainment erosion is developed. Subsequently, numerical simulations based on the observation data of the 2011 Mt. Umyeon are performed. To develop the debris flow model, the Nays2DFlood model, which is a flooding model based on the shallow water equation, is coupled with the transport diffusion of mixed sediment concentration, debris flow bottom shear stress, and entrainment erosion modules. The simulation closely reproduced the depth, flow velocity, and debris flow volume of Mt. Umyeon. In addition, the reproducibility of the simulation result with driftwood is more accurate than that without driftwood. The results of this study can facilitate in establishing measures to reduce debris disasters, thus alleviating the current increase in debris damage due to climate change.

• Proceedings of the Korea Water Resources Association Conference
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• 1998.05b
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• pp.3-3
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• 1998

In this pressentation it is argued that the heterogeneity of a hydrologic attribute which may seem to be nonstationary at one scale, may become stationary at a larger scale. The fundamental reason for transformation from nonstationarity to stationarity whith the increase in scale is the phenomenon of coarse-graining of the hydrologic processes with increasing scale. Due to the phenomenon of aliasing, a particular scale hydrologic process heterogeneity which is observed as a nonstationary process at that scale, may be observed as a stationary process at a higher(larger) scale whose size is bigger than the stationary extent of the lower scale heterogeneity. As one goes through a hierarchical sequence of larger and larger scales for observations, one would eliminate nonstationarities which emerge at some lower scales at the expense of losing information on the high frequency fluctuations of the lower scale heterogeneities which will no longer be observed at the larger sampling scales. We call this phenimenon as the "coarse-graining in hydrologic observations". In this presentation, it is also argued that by the coarse-graining of hydrologic processes due to the averaging and aliasing operations at increasing scales, the conservation laws corresponging to these scales may still be quite parsimonious, and need not be more complicated as the scales get larger. It is shown that shen a higher(larger) scale process is formed by averaging a lower(smaller) scale process in time or space, the high frequency components of the lower scale process will be eliminated by the averaging operation. Thereby, the resuliiting average hydrologic dynamics, free from the effects of the high frequency components of the lower scale process, can still be quite simple in form. This is demonstrated by means of some recent upscaling work on the solute teansport conservation equation for hetergeneous aquifers. By means of this solute transport example, it is also shown that for the ensemble average form of a hydrologic conservation equation to be equivalent to its volume-average form at any scale, the parameter functions of that conservation equation at the immediately lower scale must be ergodic.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.1
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• pp.60-69
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• 2023

Objectives: Business operators handling hazardous chemicals regulated under the Chemical Substances Control Act (CSCA) must receive permits to operate their business from the Ministry of Environment. This study analyzed the status of recent legal violation in chemical handling workplaces in Ulsan where a large volume of chemicals is handled for industrial use. Methods: A total of 557 corporations have been granted legal status as business operators in Ulsan. For all business operators, legal violations in regard to the CSCA that were discovered by the environmental office in the last five years (2018~2022) were thoroughly analyzed. Results: A total of 225 violations of the CSCA have been discovered at 165 corporations, with the violation rate accounting for approximately 27% of all business operators. In particular, 22% of the 165 violators (36 corporations) were discovered to have violated twice or more, and some business operators (6%) even violated in consecutive years. Non-compliance of facility inspection was the most frequent violation (45 cases, 20.1%), followed by non-reporting of important changes in the permitted matters (23 cases, 10.3%), non-completion of legal safety education (19 cases, 8.5%), failure to secure permission for modification in the permitted matters (18 cases, 8.0%), and failure to submit chemical transport plans (16 cases, 7.1%). Conclusions: Most of the violations could have been prevented if the field personnel had paid sufficient attention. Thus, it is fundamentally necessary to create an environment for spontaneous safety management for themselves and to strengthen individual capabilities.

• Steel and Composite Structures
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• v.45 no.1
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• pp.67-82
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• 2022

In this paper, buckling and free vibration of imperfect, functionally graded beams, including porosities, are investigated, using a higher order shear strain theory. Due to defects during the manufacturing process, micro porosities may appear in the material, hence the appearance of this imperfection in the structure. The material properties of the beams are assumed to vary regularly, with power and sigmoid law, in the direction of thickness. A novel porosity distribution affecting the functionally graded volume fraction is presented. For the compact formulation used for cementite-based materials and already used in P-FGM, we have adapted it for the distribution of S-FGM. The equations of motion in the FG beam are derived using Hamilton's principle. The boundary conditions for beam FG are assumed to be simply supported. Navier's solution is used to obtain the closed form solutions of the FG beam. The numerical results of this work are compared with those of other published research to verify accuracy and reliability. The comparisons of different shear shape functions, the influence of porosity, thickness and inhomogeneity parameters on buckling and free vibration of the FG beam are all discussed. It is established that the present work is more precise than certain theories developed previously.

• Journal of Advanced Navigation Technology
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• v.27 no.6
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• pp.699-709
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• 2023

As the global air traffic volume has shown a rapid increase, doubling every 15 years since 1977, domestic and international air traffic control services and air navigation safety facility operation management system and status review It is necessary to present the feasibility of establishing an air traffic control agency with integrated functions and establish an operating system for an independent dedicated agency to provide advanced air traffic control services in preparation for the future air transport environment. In particular, in 2021, the national ATM reformation and enhancement (NARAE) a customized comprehensive plan for operations, facilities, and systems to handle air traffic safely and efficiently by actively reflecting changes in the navigation environment such as international policies and standards as this is established, the role of the air traffic control agency becomes more important, and an improved action plan for the control and navigation operating system must be promoted.